Blueberry muffin rash in a neonate is most characteristic of congenital infection with which agent?

• A. Cytomegalovirus
• B. Rubella virus
• C. Toxoplasma gondii
• D. Herpes simplex virus

Answer: (A)

Blueberry muffin rash reflects extramedullary hematopoiesis in the newborn, producing bluish papules from scattered clusters of developing blood cells in the skin. This pattern is a classic sign of congenital infection, with cytomegalovirus being the most common agent causing it. In congenital CMV, the virus often injures the fetus and leads to systemic findings such as hepatosplenomegaly, jaundice, microcephaly, periventricular calcifications, and rash composed of purpuric lesions from extramedullary hematopoiesis.

Other infections can cause comparable skin findings, but they are not as characteristic for this presentation. Rubella is classically linked with cataracts, PDA, and sensorineural deafness; toxoplasmosis with hydrocephalus and chorioretinitis; and herpes simplex with vesicular lesions and possible disseminated disease at birth. The combination of the clinical rash pattern and the overall association with congenital CMV makes this the best match.